It is known to couple an optical fiber arranged in an optical connector to a transmitting and/or receiving module by means of a coupling unit. Light emerging from the optical fiber is thereby directed onto the photosensitive surface of a receiving element, in particular a photodiode, and/or light emitted by a transmitting element, in particular a laser diode, is coupled into the optical fiber.
In order to minimize reflections at the light-entering face or light-exiting face of the optical fiber, direct contact (physical contact) of the fiber core with an optical medium which has the same or a similar refractive index as the fiber core is advisable. In a fiber-air transition, for instance, reflections of the order of magnitude of −15 dB are produced. However, significantly better values of −27 dB are often required.
To realize such a physical contact, it is known to introduce into a coupling unit a glass fiber which is cemented into a precision ceramic pin. The one end face of the glass fiber serves as a stop face for the optical fiber of the optical connector to be coupled on. Light coupling with the transmitting and/or receiving module takes place via the other end face of the glass fiber. Among the applications for such configurations of a coupling unit are their use in optoelectronic transceivers that are produced and sold by Infineon Technologies AG under the designation “OC 48 SFF (P) transceiver”.
However, such a coupling unit is relatively expensive to produce and requires a relatively high level of assembly effort. For instance, the end face of the glass fiber that comes into direct contact with the optical fiber of the optical connector must be of very good quality. The diameter of the ceramic pin into which the glass fiber is cemented must also be configured to within an accuracy of a few μm. A large number of high-precision, relatively expensive individual parts are required.
DE 102 46 532 A1 describes a coupling unit for coupling an optical transmitting and/or receiving module to an optical fiber, in which the coupling unit forms a connecting region, which can be connected to a transmitting and/or receiving module, and a receiving region, which receives an optical fiber. Formed between these regions, in a horizontally running base plate, is a transparent coupling region, which is an integral part of the coupling unit and, like the latter, consists of plastic. Via the coupling region of transparent plastic, light is coupled directly between an optical fiber inserted into the receiving region and a coupled-on transmitting and/or receiving module.
A disadvantage of this configuration is that a coupling region made of plastic is sensitive to damage, so that a required long lifetime of the coupling unit is not always obtained.
There is a need for a coupling unit for coupling an optical transmitting and/or receiving module to an optical fiber connector which is simple and inexpensive to produce and at the same time has a coupling region which is insensitive to damage.